322 INFECTIOUS DISEASES 



driving of soiitliern cattle into and through the northern States 

 caused outbreaks of tick fever and heavy losses among northern 

 cattle. This finally resulted in the locating of the infected 

 district, and the establishment of the Texas-fever quarantine 

 line in 1891 by Dr. D. E. Salmon. 



Previous to this time Kilborne and Salmon proved that the 

 cattle tick was essential to the spread and production of the 

 disease. A further study of the life history of the tick resulted 

 in the discovery that it could not mature unless it became a para- 

 site of horses, mules, or cattle. This has led to the eradication of 

 the tick in certain sections of the South, by not allowing cattle 

 access to a pasture or lot for a certain period, and by freeing 

 the animals from ticks by hand-picking, dipping and smearing. 



The immunization of cattle that are shipped into an infected 

 district for breeding purposes is often practised. Immunity is 

 obtained by introducing the P. higeminum into the blood, either 

 by placing a few virulent young ticks upon the animal, or by 

 repeated inoculation with a very small quantity of virulent blood. 



QUESTIONS 



1. Give the cause and treatment of actinomycosis. 



2. Give the cause and treatment of emphysematous anthrax. 



3. Give the cause of tick fever; distribution of the disease and methods of 



control. 



